A self-organizing network (SON) is a communication network that may perform parameter(s) configuration, network optimization, performance measurement, troubleshooting etc. via automation mechanism, therefore, it may reduce the network deployment and configuration cost of operators, it may shorten the network optimization time, improve the operational efficiency and maintain the communication quality effectively. To fulfill the radio signal coverage rate, the interference control, the capacity, the load adjustment and so on, the radio transmission power of the base station (BS) in the SON may be adjusted adaptively to enhance the energy efficiency and/or improve the signal quality. The network architecture of SON may be centralized, distributed or hybrid. In a centralized SON, a SON controller or server centralizes the control of the BSs within the SON. A distributed SON allows each BS to control the SON operations by itself. A hybrid SON mixes architectures of the centralized SON and the distributed SON.
Nevertheless, for part of the user equipment(s) operating in an idle-mode (hereafter called “idle UE”) that already registered and camped on a BS, the mobile network system and the BS is unable to obtain the exact location of the aforementioned idle UE. The location of an idle UE is explored only when the idle UE is requesting for a connection service or is been tracked (for instance, is responding a paging message). Therefore, when the transmission power of a BS in a SON is decreased, the idle UE located at the boundary of the signal coverage of the BS may lose the BS on which the idle UE originally camped. If the idle UE fails to discover a connectable BS via a BS reselection procedure, the idle UE will fail to connect any network thereafter. In other words, the location of the idle UE is becoming a coverage hole. Or, if the transmission power of a BS is increased so that the coverage covers an idle UE camping on a vicinity BS, the idle UE may suffer a larger interference when it would like to regain a connection.
Therefore, it is becoming a design consideration on how to avoid a negative influence to an idle UE due to the adjustment of the transmission power or the signal coverage of a BS in a SON.